1. Field of the Invention
The present invention relates to an electrical latch for a vehicle door, in particular of the type utilizing a double pawl arrangement.
2. Brief Description of Related Art
As it is known, one of the defining characteristics of an electrical door latch is that it does not have mechanical linkages to outside and inside door handles. Instead, the door is released by an actuator in response to an electric signal coming from the handles.
Electrical door latches using double pawl arrangements normally comprise:                a ratchet biased by a spring into a release position, wherein the ratchet is positioned to receive or release a striker fixed to a door post, and which can be moved to a partially locked or first-click position and a fully locked or second-click position, in which the striker is increasingly retained inside the ratchet and prevented from withdrawing;        a primary pawl movable between a ratchet checking position, wherein the primary pawl is positioned to keep the ratchet in the partially locked or fully locked positions, and a ratchet release position, wherein the primary pawl permits the movement of the ratchet out of the partially locked or fully locked positions;        an auxiliary ratchet operatively connected to the primary pawl and movable between an enabling position, in which the primary pawl is enabled to move to its ratchet checking position, and a disabling position, in which the auxiliary ratchet positions the primary pawl to its ratchet release position;        a secondary pawl movable between an auxiliary ratchet holding position, in which the secondary pawl is positioned to hold the auxiliary ratchet in its enabling position, and an auxiliary ratchet release position, in which the secondary pawl is positioned to permit movement of the auxiliary ratchet to its disabling position; and        an electrically-operated actuator which can be selectively activated for moving the secondary pawl to the auxiliary ratchet release position and the auxiliary ratchet to the enabling position.        
The double pawl arrangement consists in establishing a connection of a first set formed by the ratchet and the primary pawl with a second set formed by the auxiliary ratchet and the secondary pawl.
The connection is configured such that only a portion of the forces experienced by the first set are applied to the second set, thus requiring only a relatively low effort to release the latch.
In case of failure of the actuator or in case no energy were available in the vehicle, the known electrical latches may be normally opened by inside and outside emergency release mechanisms (which can be also indicated as inside and outside back-up mechanisms).
Both these mechanisms can be manually operated by the user for releasing the ratchet from the striker.
Known electrical latches can be also provided with an outside emergency lock mechanism for permitting closure of the door even in emergency conditions.
The outside emergency release and lock mechanisms can be activated by acting in opposite directions on the same outside control element, for instance an external key.
During the outside emergency release operation, an action is impressed to the secondary pawl to move it to the auxiliary ratchet release position, so permitting the auxiliary ratchet to reach the disabling position under the action of a spring and to free the primary pawl from the ratchet.
In a different manner, in order to obtain the full lock of the latch from the outside of the vehicle in emergency conditions, an action has to be impressed to the auxiliary ratchet to move it to the enabling position after the ratchet has reached the partially locked position on the striker. This means that it is first necessary to pull the door to the doorpost and then to move the auxiliary ratchet to the enabling position acting on the external key.
In emergency conditions, it is however possible for the user to move the external key in the lock direction when the door is still open; in this hypothetical case, if the key were extracted from the relative seat on the door and put inside the vehicle, an undesired closure of the door would result in the impossibility of reopening it.